In the production of oil a pumping unit is driven by an alternating current (AC) electric motor energized by alternating current from an AC electric power grid to pump oil from the oil well. A well manager unit is used to monitor and regulate the operation of the well in response to conditions in the well. For example, well parameters such as the speed of the motor, the amount of fill of the pump, amount of gas in the well, down-hole well pressure, etc. are monitored and controlled as required. The commonly used rod pumps are a long-stroke pumping unit and a beam pumping unit. In both cases, it is necessary to regulate the speed of the electric motor to avoid creating compression of the pumping unit's rod or otherwise damaging equipment. This may require braking to slow the motor speed and then increasing the motor speed, depending on the position of the rod during the course of each stroke cycle. Each stroke cycle includes an upstroke to a predetermined top rod position where the direction of movement of the rod reverses and begins a downstroke until the rod reaches a predetermined bottom rod position. Then the rod's upstroke is again initiated. Normally braking is accomplished by directing excess electrical energy through resistors that dissipate this electrical energy as heat to the surrounding environment. This, however, is a fire hazard. It is also a waste of electrical energy.
This background discussion is not intended to be an admission of prior art.